Visual Pathways

Question 1

What are the parts of light reflex arch?

Answer 1

Optic nerve -> Superior Colliculi (Pretectum n.) -> 3 parasympathetic n. (Edinger - Westphal n.) -> ciliary ganglion -> m. sphincter pupillary

Question 2

What are the components of Accommodation - Convergence Reaction?

Answer 2

1. Accommodation (PANS -> ciliary m. contraction -> suspensory ligaments relaxation -> lens becomes rounder)
2. Convergence (contraction of both medial rectus m.)
3. Miosis (PANS -> pupillary sphincter m.)

Question 3

What is Argyll Robertson pupil (pupillary

light-near dissociation)?

Answer 3

• No direct or consensual light reflex;
accommodation-convergence intact
• Seen in neurosyphilis, diabetes

Question 4

What is Relative afferent (Marcus Gunn) pupil?

Answer 4

• Lesion of afferent limb of pupillary light reflex;
diagnosis made with swinging flashlight
• Shine light in Marcus Gunn pupil → pupils do
not constrict fully
• Shine light in normal eye → pupils constrict fully
• Shine light immediately again in affected eye
→ apparent dilation of both pupils because
stimulus carried through that CN II is weaker;
seen in multiple sclerosis

Question 5

What is Adie pupil?

Answer 5

Dilated pupil that reacts sluggishly to light, but
better to accommodation; often seen in women
and often associated with loss of knee jerks.
Ciliary ganglion lesion

Question 6

Which intrinsic eye muscles do you know? What receptors do the have?

Answer 6

Pupillary sphincter ms. (iris) M3 receptor (PANS)

Radial dilator ms. (iris) α receptor (SANS)

Ciliary ms. M3 receptor (PANS) (Contraction→accommodation for near vision
Relaxation → focus for far vision)

Ciliary body epithelium β receptor (SANS) (Secretion of
aqueous humor)

Question 7

How does visual pathway come?

Answer 7

1 and 2 neurons are in Retina -> optic nerve -> optic chiasm (medial fibers crosses, lateral - don’t) -> optic tract -> LGB (3 neuron) -> temporal (Meyer’s loop, lower retina) and parietel (upper retina) fibers -> lingual and cuneus gyrus respectively

Question 8

What is Rule of “3L”?

Answer 8

Lower retina in Lateral fibers forming Meyer’s Loop

Question 9

What divides lingual and cuneus gyrus?

Answer 9

Calcarine sulcus

Question 10

What is Parinaud syndrome?

Answer 10

Pineal gland tumor -> superior colliculi lesion -> vertical gaze palsy

Question 11

What is the pathogenesis of Uncal herniation?

Answer 11

High ICP -> uncal herniation (temporal lobe) -> Oculomotor nerve lesion